In-line roller skates basically can be grouped into five types that have different designs and characteristics to achieve different functions as follows:
1. Leisure skates: they are the most common type, and usually consist of an inner pad and a shoe cap. They mainly aim at providing comfort and safety, and are designed for recreational use for the general public. The wheels and bearings are replaceable according to user's preferences and requirements. 2. Stunt skates: whether with a U-shaped deck or jumping board, they have special design requirements. As they are used for many jumping actions, they require a balanced base deck and a sturdy and well-covered inner pad to avoid exercise injury. They also are of a smaller size and have a flat and wider shape to make landing on the ground more stable. They usually are coupled with straps and lateral sliding flaps and a base deck guarding flap. 3. Hockey skates: they usually adopt an integrated form without inner pad so that they enable the foot to fit the shoe more closely, and so that forward motion and goal shooting may be exercised quickly. Their material is mainly leather. 4. Speeding skates: generally use high class wheels and more precise bearings, and usually have five wheels. The base deck mostly is made of aluminum alloy. The wheels have diameters ranging from 76 mm to 80 mm, and usually are formed in a sharp profile to reduce friction force with the ground surface. 5. Figure skates: usually have a base deck coupling with three or four wheels, and have a stop at the front end of the base deck to facilitate performing pivot and leap actions.
The adjustable roller skates now available on the market as shown in FIGS. 1 and 2 mainly have a straight slot or anchor holes on the truck or the lateral side. There is a sliding mechanism located on the bottom of the roller skate. Screws are coupled on the straight slot or anchor holes for anchoring the position. When the screws are unfastened, the shoe cap may be slid freely on the truck to adjust the dimension. Once the dimension is decided, the screws are fastened to the straight slot or anchor holes. Hence the dimension of the shoe cap may be adjusted for more than one person to wear. As the anchor holes have limited intervals, the dimension adjusting range of the roller skates also is limited. The straight slot does not have such a problem, and thus can adjust the dimension more freely. However, the screws are difficult to fasten and easy to get lost. All of this often causes inconvenience when in use.